At high frequencies, for example, at or above 1 GHz the propagation of electrical signals along conducting wires is hampered by the effect of losses. Such losses typically cause attenuation as well as dispersion of the signals. If the signal represents a stream of digital data, dispersion causes smoothing of temporal edges, limiting the rate at which digital symbols can be transmitted without intersymbol interference. Attenuation also makes it difficult to identify digital symbols.
It has been found useful to use a transmission line for a variety of purposes, one such purpose being as a delay line and/or finite impulse response filters. However, attenuation and/or dispersion of the signal at high frequencies, limits the usefulness of transmission lines as delay line elements.
One system for controlling attenuation and/or dispersion in a primary conductor is by use of an auxiliary conductor inductively coupled to the primary conductor. The auxiliary conductor is driven by the primary conductor through an active shunt network distributed along the transmission line. In a variation of this system, two pairs of conductors including a first and second primary conductor and a first and second auxiliary conductor can be operated in differential mode. As will be seen later, the distributed active shunt network can be particularly simple in differential mode.